Conventional mouse experiments are hampered by at least three factors. First, most experiments involve humans handling mice. As humans are a mouse predator, this means that data from laboratory mice is inherently tainted by the stress and fear responses inherent in the measurement procedures. Secondly, because many experiments involve labor-intensive data collection from the mice, most mice are only generating useful data for a very small portion of the day. In the case of behavioral experiments a further confound is often that data are taken during daylight hours when a mouse would normally be asleep. Further, experiments involving continuous data collection (such as feeding behavior) require animals to be singly housed, which is a further confounding source of stress; or they require only one data-generating animal per group (e.g. telemetry) which needlessly increases the number of animals housed. Lab mouse environments are typically unnatural, and typically present mice with a broad array of stimuli which in the wild would signal a threat to survival or reproduction; or which disrupt cues or sensory signals essential to normal mouse physiology and behavior (Olsson & Dahlborn 2002; Sherwin 2002; Latham & Mason 2004).
Environmental enrichments include changes in cage design, cage furniture, bedding, husbandry, or other aspects of animal care, that may facilitate normal behavior and allow animals to, for example, regulate and control stressors in their environment (Olsson & Dahlborn 2002; Garner 2005). Enrichments may improve, for example but not limited to, the welfare of laboratory animals, and the quality of scientific data they provide (Würbel 2001; Olsson & Dahlborn 2002; Garner 2005).
A naturalistic system, such as a housing or experimental capture system, is disclosed which may, among other things, provide a general system for the feeding, census taking, daily monitoring (through photographs, temperature, weight, etc), and capture, if necessary, of mice, rabbits, dogs, primates, and other laboratory animals, with limited to no human intervention. This system may also be adapted to a wildlife or zoo environment. Although mice are discussed herein, the system is not limited to and may be adapted to other animals, birds, reptiles, and etc.
There are many ways in which feeding behavior may be studied, ranging from the general, such as total 24-hour food intake, to the specific, such as meal analysis (Ravussin & Bouchard 2000). Meals are considered the functional units of ingestion. The parameters measured in meal pattern analysis may include, but are not limited to, meal frequency, meal duration, meal size and the inter-meal interval. By contrast, microstructure analysis of ingestive behavior, may examine, among other things, the licks, bites, and chews of a meal (Kissileff 2000).
Techniques for analyzing the meal patterns and microstructure of food intake may, for example, feed animals using automated food dispensers, which may give precise measurements of pellet or liquid food (Davis 1989; Kissileff 2000). These precise, in-depth measurements may extend the findings of meal patterns and the microstructure of meals, give a better idea of how ingestive behavior occurs, develop the relationships between meal number and hunger or meal duration and satiation, and provide evidence of motivational processes, such as appetite, and the underlying mechanisms of feeding behavior (Smith 2000; Strubbe & Woods 2004).
These techniques typically rely on the social isolation of each animal to ensure that the identity of each animal feeding from the automatic feeder is known. When animals are studied under situations fundamentally different from their natural conditions the external validity of the results may be limited (Würbel 2000; Würbel 2001), for example, because the stress of social isolation may affect the animal's physiology and hence its feeding behavior. For instance, socially isolated rats gain less weight than group housed rats, as well as showing many other signs of stress (Perello et al. 2006).
Few physiological variables in animals are unaffected by stress (Moberg & Mench 2000), and psychological components of a stressor can ultimately determine the magnitude of its impact (Weiss 1971). Indeed, the breadth of systems affected by stress is neatly illustrated by the breadth of measures taken in stress studies, from hormonal titers, to heart rate, to immune function, to gross organ weights, to abnormal behavior (e.g. Hurst et al. 1999). Handling itself is a stressor, animals differ greatly in response to handling, and experimenters differ greatly in their handling styles. As a result, interactions between the animal and the experimenter add a great deal of noise to experimental outcomes, which, mediated by stress responses can potentially affect a wide variety of experimental outcomes. Experimenters themselves may be a source of experimental noise in many mouse experiments (e.g. Chesler et al. 2002). Accordingly, handling or experimenter can markedly affect the outcome of a wide variety of experiments (e.g. Andrews & File 1993; Ryabinin et al. 1999; Chesler et al. 2002; Gariepy et al. 2002; Chou-Green et al. 2003; Hale et al. 2003; Sternberg & Ridgway 2003; Bayne 2005).
This present invention addresses the above-described problems and limitations by providing methodologies aimed at reducing experimental variability or bias introduced by differences between experimenters in their handling of animals and in the way they take measurements, thereby reducing or eliminating much of the variability introduced by differences between animals in the degree of their stress response in response to being handled for experimental procedures.